1. Field of the Inventions
The present inventions relate generally to catheters.
2. Description of the Related Art Catheters, which are in widespread medical use today, allow physicians to gain access into interior regions of the body in a minimally invasive manner. Catheters are frequently used to advance electrodes, biopsy devices, and other operative elements through bodily lumens to an intended treatment site. In cardiac treatment, for example, the catheter is advanced through a main vein or artery into the region of the heart that is to be treated.
Although precise control of catheter movement is of paramount importance in all catheter-based procedures, the need for careful and precise control over the catheter is especially critical during certain procedures concerning the heart. These procedures, called electrophysiological therapy, are becoming more widespread for treating cardiac rhythm disturbances. Cardiac tissue coagulation (sometimes referred to as xe2x80x9cablationxe2x80x9d), where therapeutic lesions are formed in cardiac tissue, is one procedure in which the ability to precisely position the distal end of the catheter is especially important. Incremental distal end movements of 1 mm to precisely position electrode(s) carried on or near the catheter tip are not uncommon and it can take up to an hour to precisely position the tip. In those instances where multiple electrode distal assemblies are employed, it is important that all of the electrodes achieve intimate tissue contact.
Some catheters are steerable in that the distal tip can be manipulated with a distal tip steering mechanism that is operably connected to the catheter handle by a steering control wire. The steering mechanism consists primarily of a center support (also referred to as a xe2x80x9csteering springxe2x80x9d). The center support is mounted on the distal end of an elongate guide coil and extends to the distal tip of the catheter. The guide coil extends to the proximal end of the catheter. A ferrule, which is a cap-like device that may be positioned on the distal end of the guide coil, is used to mount the center support. The ferrule includes a slot for the center support and one or more openings through which the steering wires pass.
Steerable catheters also typically include a catheter body formed from two tubular parts, or members. The proximal member is relatively long and is attached to the handle, while the distal member, which is relatively short, carries the electrodes or other operative elements. In addition, the proximal member is typically formed from material, such as braided Pebax(copyright), which has better torque transmission properties than the distal member, which is typically formed from a softer, more flexible material such as Pebax(copyright) that is better for steering.
In addition to steerability, torque transmission is important because physicians will often attempt to control the position of the distal end of the catheter by rotating the handle at the proximal end. The ability of the physician to precisely control the location of the distal end is directly related to the fidelity of the catheter""s transmission of torsional forces exerted on the proximal end to the distal end. Torque is transmitted to the tip from the proximal member by way of the distal member. Torque is also transmitted to the tip from the guide coil by way of the center support. To that end, the ferrule prevents rotation of the center support relative to the guide coil so that torque transfer can take place.
The inventors herein have determined that conventional steerable catheters are susceptible to improvement. More specifically, the inventors herein have determined that the configuration of the distal tip steering mechanisms in conventional steerable catheters is unnecessarily costly. For example, the inventors herein have determined that the configuration of the steering center support in conventional steerable catheters necessitates the use of a ferrule to mount the center support within the catheter.
Accordingly, the general object of the present inventions is to provide a catheter that avoids, for practical purposes, the aforementioned problems. One object of the present inventions is to provide a steerable catheter that can be manufactured in a more economical manner than conventional steerable catheters. Another object of the present invention is to provide a steering center support that can be mounted within the catheter without the use of a ferrule.
In order to accomplish some of these and other objectives, a center support in accordance with one embodiment of a present invention includes a steering member and a mounting member integral with the steering member. Such a center support provides a number of advantages over conventional center supports. For example, the integral mounting member allows the present center support to be mounted directly onto a guide coil or other internal support member. As such, the present center support eliminates the need for the ferrules that were required to mount the center supports onto the guide coils in conventional catheters. The integral mounting member also allows the center support to be fixedly secured to the guide coil or other internal support member, which results in high fidelity torque transmission from the internal support member to the catheter tip.